Lubricants



Patented Mar. 16,1954

LUBRICANTS Lawson W. Mixon, Hammond, and Roger W. Watson, Highland,Ind., assignors to Standard Oil Company, Chicago, 111., a

diana corporation of In- No Drawing. Application November 30, 1949,Serial No. 130,372

This invention pertains to improvements in lubricant compositions, andmore particularly is directed to improving the temperature-viscositycharacteristics of hydrocarbon oil lubricants.

It is known that the viscosity of certain types of hydrocarbon oils isgreatly affected by temperature changes, thus it is known that theviscosity of highly parafiinic oils does not change as greatly and asrapidly as do naphthenic oils with changes in temperature. Thisviscosity-temperature relationship is measured by the viscosity index(V. I.) of the oil. Oils which change little in viscosity with increasein temperature have a greater viscosity index than do oils whoseviscosity is materially affected by increase in temperature. Thus,paraifinic oils have, in general, higher viscosity indices than donaphthenic oils. Where wide variations in operating temperature areencountered, for example, in automobile and aircraft engine lubrication,the viscosity-temperature coefiicient (V. I.) of the lubricant is ofgreat importance, and hence hydrocarbon oils which exhibit a minimumchange in viscosity under such operating conditions, i. e., have a highviscosity index (V. 1.), are highly desirable.

It is an object of the present invention to provide a hydrocarbon oillubricant having improved viscosity-temperature characteristics. Anotherobject of the invention is to provide a, lubricating oil compositionwhose viscosity changes little with increase in temperature. Still afurther object of the invention is to provide a hydrocarbon oillubricant composition having improved viscosity-temperature coefficient.Other objects and advantages of the invention will become apparent fromthe following description thereof.

In-accordance with the present invention the viscosity-temperaturecoeiiicient of hydrocarbon oils, especially of the lubricating oilrange, is greatly improved by the addition thereto of a small amount ofan oil-soluble polymerhaving a molecular weight of at least about 1000,and preferably in therange of from about 5000 to about 50,000 of anester of an olefin dicarboxylic acid having the general formula inwhichR and R are alkyl radicals of at least 6 Claims. (Cl. 252-56)compositions in amounts sufficient to impart to the oil the desiredviscosity-temperature characteristics; amounts in the range of fromabout 0.1% to about 20%, and preferably from about 0.5% to about 10%, byweight, are usually sufficient to obtain the desired result.

The esters of itaconic acid can be prepared by direct esterification ofthe itaconic acid with the selected saturated alcohol in the presence01' esterification catalysts, such as para-toluene sulfonic acid,metallic sodium, potassium carbonate, sulfonic acid, sodium acidsulfate, etc. The alcohol used for the esterification is preferably onehaving at least 4 carbon atoms, and preferably 'at least 8 carbon atoms,for example, butyl alco-' hol, amyl alcohol, octyl alcohol, nonylalcohol, decyl alcohol, dodecyl alcohol, cetyl alcohol, octadecylalcohol, stearyl alcohol, myricyl alcohol, etc. The mixed esters may beprepared by effecting the reaction between an itaconic monoester acidchloride and the selected alcohol in the presence or absence of aninhibiting agent, such as phenolic bodies, copper, etc. Other methods ofpreparing mixed esters are, (1) from. an itaconic mono-acid chloride andone of the select saturated alcohols, followed by direct esterificationof the other acid radical by another selected saturated alcohol of thedesired carbon chain length, and (2) by the esterification of the acidwith mixtures of alcohols.

The alkyl esters of aconitic acid can be prepared by the acetylation ofthe corresponding ester of citric acid with acetic anhydride followed bydehydration to form the. corresponding aconitate and acetic acid. Forexample, tributyl aconitate is prepared by heating tributyl citrate withacetic anhydride for one hour at about 310 F. in the presence ofphosphoric acid as the catalyst, and heating the resultant product at atemperature of about 795 F.

Polymers of the herein described esters ofole fin polycarboxylic acidscan be prepared by polymerizing the pure ester at a temperature of fromabout 100 F. to about 350 F. in the presence of a catalyst, such as forexample, oxygen, ozone, hydrogen peroxide, sulfuric acid, aluminumchloride, boron fluoride, aliphatic acyl peroxides, such as acetylperoxide, stearyl peroxide and the peroxides of the aromatic acids, suchas for example, benzoyl peroxide; the preferred catalyst being the'benzoyl peroxide.

The method of polymerizing the dialkyl itaconate is illustrated by thefollowing example:

EXAMPLE I A flask containing about 100 g. of di-2 ethylhexyl itaconatein which is dissolved 0.1% benzoyl peroxide is flushed for one hour withpurified nitrogen, sealed under this atmosphere and warmed for 72 hoursat -80 C. The product is a colorless to pale. yellow oil-solublesemi-solid having a molecular weight in the range of about 10,000.

As mentioned above, instead of using a poly mer and/or copolymer of thealkyl esters of itaconic acid, copolymers of such esters with alkylaconitates and/or alkyl methacrylates can also be employed. The alkyl'aconitate and. alkyl methacrylate are preferably those having at least4 carbon atoms in the alkyl group and preferably from about 4 to about18 carbon atoms in the alkyl group. Examples of suitable methacrylatesare butyl methacrylates, heptyl methacrylate, octyl methacrylate,2-ethylhexyl methacryl-ate, nonyl methacrylate, decyl methacrylate,dodecyl .(lauryl). methaerylate, cetyl methacrylate, octa: decylmethacrylate, etc. Examples of. suitable alkyl, aconitates, are tributylaconitate, trihexyl 'aconitate trinonyl aconitate, tridodecyl aconitate,trioctadecyl aconitate,v etc.

The copolymerization of the herein described alkyl esters of itaconicacid with. alkyl aconitates and/or alkyl methacrylates can be carriedout by heating a mixture of the olefin dicarboxylic acid ester with thealkyl methacrylate and/or alkyl aconitate in the ratio of from about 1:1to 2:1, at a temperature of, from about F. to about 200 F... andpreferably from about 80 F. to about 160 F., in the presence of. a.catalyst, for example, a peroxide of the organic acid series, such asbenzoyl peroxide. The polymerization is continued until a product.having, the desired molecular weight, namely at least 1000, andpreferably from about, 5000, to about 50,000, is obtained. Thecopolymerization of an alkyl methacrylate and a dialkyl ester ofitaconic acid is illustrated by the following example:

EXAMPLE H Y A flask containing 100 g. of the mixed monomers dioctylitaconate and octyl methacrylates in the mole ratio of 1:1 together with05% benzoyl peroxide was flashed with purified nitrogen for one hour,sealed under this atmosphere and heated 48 hours at 60 C. The productwas a pale yellow oil-soluble solid.

The, effectiveness of the copolymers of dialkyl esters of itaconic acidand alkyl esters of methacrylic acid having an average molecular weightof about 7,000 is illustrated by the, following data which were obtainedby determining'the amount of the copolymer of dinonyl itaconic. andvarious alkyl methacrylates. were required to obtain a 140 viscosityindex using as a base, oil a. petroleum oil having a Saybolt Universalviscosity at 100 F. of about 105 seconds and a viscosity index of about70. l

Copolymers or dinonyl itaconate and math.-

{Two moles of itaconate/one mole of methacrylate otherwise 1:1. Dinonylltaoonate polymers in concentration of 0.5% in the above base oilmcreased the viscosity index from 70 to 125.

about 10 carbon. atoms.

4 The herein described polymers and copolymers can be used in normallyliquid lubricant compositions comprising a major proportion of ahydrocarbon oil, for example petroleum oils, synthetic hydrocarbon oils,etc., as well as in normally semisolid and solid lubricants, such asgreases. The composition, can contain in addition other additives, suchas pourpoint depressants, antioxidants, metal deactivators, E. P.agents, etc.

While we have described our invention by reference to certain examplesthereof the invention is not limited by'the same, but includes withinits scope such modifications as come within the spirit of the appendedclaims.

We claim:

1. A normally liquid lubricant composition comprising a major proportionof a hydrocarbon oil and from about 0.1% to about.20%, by weight, of acopolymer of a, dialkyl itaconate in which the alkyl groups contain fromabout. 4 to about 30 carbon atoms, said dialkyl itaconate being an esterof a saturated alcohol and itaconate acid, and an allsyl methacrylate inwhich the alkyl group contains from about 4 to about 18 carbon atoms,said copolymer having a, molecular weight of from about 1000 to about50,000.

2. A normally liquid lubricant composition as described in claim 1 inwhich the alkyl ester of the itaconic acid and the alkyl methacrylateare employed in the ratio of from about 2:1 to about 1:1.

3. A normally liquid lubricant composition comprising a major proportionof a. hydrocarbon oil and from about 0.1% to about 20% by weight of acopolymer of a dialkyl itaconate having from about 8 to about 30 carbonatoms in the, alkyl groups, said dialkyl itaconate being an ester of asaturated alcohol and itaconic acid, and an alkyl methacrylate, havingfrom about 4. to; about 18 carbon atoms in the alkyl group, saidoopolymer having a molecular weight within the range of from about 500.0to about 50,000..

4. A normally liquid lubricant composition described in claim 3 in whichthe dialkyl itaconate is dinonyl, itaconate and the alkyl methacrylateis heptyl methacrylate.

5. A normally liquid lubricant composition described in claim 3 inwhichthe dialkyl itaconate is dioctyl itaconate and the alkylmethacrylateis octylmethacrylate.

6. A lubricating oil composition consisting essentially of a hydrocarbonoil and from. about 0.1% to about 20% by weight, of a copolymer of adialkyl itaconate in; which the alkyl; groups contain about 10 carbonatoms and an: alkyl methacrylate in which the alkyl groupcontains LAWSONW. MIXON. ROGER w. WATSON.

References Cited the ille of this patent UNITED STATES PATENTS NumberName Date 2,020,714 Wulff Nov.:12,*1935 I 2,091,627 BrusonAug'.'3=1'..1'937 2,279,883 DAlelio Apr.14, 1042 2,366,517 GleasonJan.'2, 1945 2,375,516 Blair May 8', 1945 2,380,304 Gleason July 10,1945 2,509,203

Bartlett May 30, 1950

1. A NORMALLY LIQUID LUBRICANT COMPOSITION COMPRISING A MAJOR PROPORTIONOF A HYDROCARBON OIL AND FROM ABOUT 0.1% TO ABOUT 20%, BY WEIGHT, OF ACOPOLYMER OF A DIALKYL ITACONATE IN WHICH THE ALKYL GROUPS CONTAIN FROMABOUT 4 TO ABOUT 30 CARBON ATOMS, SAID DIALKYL ITACONATE BEING AN ESTEROF A SATURATED ALCOHOL AND ITACONATE ACID, AND AN ALKYL METHACRYLATE INWHICH THE ALKYL GROUP CONTAINS FROM ABOUT 4 TO ABOUT 18 CARBON ATOMS,SAID COPOLYMER HAVING A MOLECULAR WEIGHT OF FROM ABOUT 1000 TO ABOUT50,000.